High resolution map of the normal retinal thickness at the posterior pole

Purpose. Objective and sensitive measurements of the retinal thickness at the posterior pole are useful to detect and delineate macular edema or retinal atrophy. We have developed a method of rapid mapping of the retinal thickness and applied it to the study of the normal thickness at the posterior pole. Methods. The measurements were performed on a commercial (Talia Technology Ltd, Israel) prototype of the Retinal Thickness Analyzer (RTA) designed for rapid scanning retinal thickness analysis. A green (540 nm) laser slit was focused on the retina via a scanning mirror placed at the conjugate plane of the pupil. The intersection between the laser slit and the retina was viewed at an angle and 10 optical sections were digitized in 200 msec via a video camera. Nine macular areas were scanned to cover the central 20° of the posterior pole. The images were analyzed by an operatorfree algorithm to yield a map of the retinal thickness. The posterior pole was mapped in 29 normal subjects 19 to 76 years old (mean 48 years). Results. The retinal thickness varied according to the known anatomical distribution of photoreceptors, ganglion cells and nerve fibers yielding a C shaped maximal thickness around the fovea. The variation in retinal thickness among the subjects, over the whole posterior pole, was ±20nm and the local variation was, on average, ±29u,m. No significant differences were found among the various locations. Age, gender and race did not affect the values by more than 20jim. Conclusion. Rapid scanning thickness analysis with the RTA provides a detailed map of the retinal thickness at the posterior pole. The similarity between the maps of normal subjects of different ages, gender and race indicates that the method can provide a sensitive detection of pathological thickening or thinning of the retina.

Duke Scholars

Author Sanjay Girdhari Asrani Ophthalmology, Glaucoma